FIG. 1 illustrates a conventional satellite communications network 100 which is used to transmit data from a terrestrial sender 110, located at the “central site” 102, via the satellite 118 to a number of receivers 112-116 at “remote sites” 104-108. The transmitted data may be binary encoded files or some other file format. The network 100 includes the central site 102, the associated satellite transponder 110, the satellite 118, and the remote sites 104, 106, 108, with their respective receivers 112, 114, 116. Only three remote sites are shown in FIG. 1, however, a typical satellite communications network may transmit data to thousands of receivers. A customer of the network 100 purchases a certain amount of bandwidth on the satellite transponder 110, typically for extended periods of time. E.g., a customer might lease bandwidth in the amount of 10 Mega bits per second (Mbps) on a transponder with a total capacity of 36 Mbps, for one or several months at a time.
Typically, a customer will transmit files from his/her central site 102 to one, some, or all remote sites 104-108, as soon as the file is available for transmission, and typically, all file transmissions are made at a fixed bandwidth. The bandwidth setting can be limited from above, by (A) the remaining available bandwidth on the transponder 110, given that on some systems, more than one file can be transmitted simultaneously from one transponder to (typically) disjunct sets of receivers, by (B) the maximum receive bit rate of the slowest receivers 112-116 addressed by the file transmission in question and by (C), maximum encoding rates of forward error correction equipment. The bandwidth setting for any one file transmission may also have to be limited from below, because most files have a Latest Delivery Time (LTD), i.e., the deadline by which the customer wants the file received correctly by all addressed remote sites. Missing that deadline would imply financial loss to the customer, and may make a file transmission obsolete. However, setting the bandwidth for all file transmission slow enough to accommodate the slowest receiver addressed by a particular transmission, will often place an unnecessarily restrictive upper limit on the bandwidth from many other file transmissions, which may not address the slowest receiver in the first transmission.
Moreover a typical file transmission system will not account for the fact that often, the amount of bandwidth available on the transponder for file transmissions is not constant, even though the total amount of bandwidth leased by the customer is. This is because some of that leased bandwidth may also be used, at times, for transmissions and other data, such as Live Video Streams (LVS), which require a fixed and very stable amount of bandwidth. To avoid over subscription of transponder bandwidth, a conventional file transmission system will typically limit itself to never use more bandwidth for file transmissions than what is available while the video stream is being transmitted, i.e., the worst-case scenario for file transmissions, implying that the amount of bandwidth reserved for life video goes to waste when none is being transmitted, which may be most the time. Waste of transponder bandwidth is costly, and is especially undesirable if, at the same time, some files cannot be transmitted early enough to meet their delivery deadlines.
Accordingly, there exists a need for a method and system for providing an improved bandwidth allocation scheduler for media delivery. The method and system should allocate bandwidth such that waste in bandwidth is reduced, thus reducing the cost for the customer. The present invention addresses such a need.